Some boxes are crap (And normally the cheapest ones) and some are great (the more expensive ones) it depends on what you really want.
If you only care about what's currently on and the next show coming up, any box would do, but if you like a week-long program guide, with event timers and such, the Dish DTVPal is a great bet. it all depends on what you desire.
The top three boxes from my own experience are:
1. Dish DTVPal Plus ($50-70), has a week-long program guide, just like their satellite receivers, and an event timer for a VCR.
2. Zenith DTT901/Insignia clone (Same box, excellent tuner lock, and is $10-20 cheaper than the DTVPal, but only has a simple guide which shows what's currently on and the next show, but allows you to browse the same on other channels without changing the one you're watching.)
3. Digital Stream (@Radioshack) (it's the same price range of the Dish DTVPal, but also sports a great tuner for distant stations. although it has a fully-featured weeklong program guide, it only gives data for the current channel selected; you have to change channels to get the data for those)
Other boxes exist, both good and bad, but we'd have to write a technical manual to list the pro's and con's of all of them.
I have tried a couple and from what I can see is that it is all about the functions. Some have better TVGuide Menus and some let you set a reminder timer for programs so it will change the ch. for you if you forget. Also some of the cheaper ones have the simplest remotes. I have the DTVPal DVR and the DTVPal Plus I think its the plus or replaced the 40. Anyway on this one the menu is the best I have seen and the TVGuide displays info and has a reminder timer. Down side is the remote does not have a TV Power switch. Up side is that a Dish Network remote that controls Satalite DVR's will work with it. Do a google search for differnt boxes and click on google images to see pics of them. Sometimes people post pics of their TV screen and that will help you with what looks the easiest or hardest and has the menu screen you would be happy with. I like DTVPal converters...I don't work for them...just like them best.